Low molecular weight acrylic copolymer latexes for donor elements in the thermal printing of color filters

ABSTRACT

A donor element is described for use in a thermal imaging process. The donor element includes a support; a heating layer, and a colorant containing thermally imageable layer comprising a crosslinkable binder having a number average molecular weight of about 1,500 to about 70,000. A process for making a color filter using a thermal imaging process, and a liquid crystal display using this color filter are also described.

FIELD OF THE INVENTION

This invention relates to improved products and processes for effectinglaser-induced thermal transfer imaging in the formation of colorfilters. The invention is of particular utility in the formation ofcolor filters in high resolution liquid crystal displays.

BACKGROUND OF THE INVENTION

Liquid crystal display (LCD) devices have become increasingly importantin displays that require very low consumption of electrical power orwhere the environment dictates a lightweight, planar, flat surface. Forexample, LCDs are used in display devices such as wristwatches, pocketand personal computers, flat panel television displays and aircraftcockpit displays. When there is a need to incorporate a color displaycapability into such display devices, a component called a color filteris used. For the device to have color capability, each LCD pixel isaligned with a color area, typically red, green, or blue, of a colorfilter array. Depending upon the image to be displayed, one or more ofthe pixel electrodes is energized during display operation to allow fulllight, no light, or partial light to be transmitted through the colorfilter area associated with that pixel. The image perceived by a user isa blend of colors formed by the transmission of light through adjacentcolor filter areas.

A major contributor to the cost of color LCDs is the color filter. Fourcolor filter manufacturing methods are known in the art, viz., dyegelatin, pigmented photoresist, electrodeposition and printing. Thepigmented photoresist method offers the best trade-off of degradationresistance, optical properties, and flexibility along with highresolution, and is generally preferred. While conventionalphotolithographic materials and methods may be employed in thephotoresist method, it suffers from the high cost and inconvenienceassociated with numerous process steps, some involving wet chemistry.

Laser-induced thermal transfer processes are well-known in applicationssuch as color proofing and lithography and have been described in, forexample, Baldock, U.K. Patent 2,083,726; DeBoer, U.S. Pat. No.4,942,141; Kellogg, U.S. Pat. No. 5,019,549; Evans, U.S. Pat. No.4,948,776; Foley et al., U.S. Pat. No. 5,156,938; Ellis et al., U.S.Pat. No. 5,171,650; and Koshizuka et al., U.S. Pat. No. 4,643,917.

As is known in the art, laser-induced processes use a laserableassemblage comprising (a) a donor element containing the material to betransferred in contact with (b) a receiver element. The laserableassemblage is exposed to a laser, usually a suitable spatially modulatednear-infrared laser, resulting in transfer of material from the donorelement to the receiver element. To form an image, exposure takes placeover a small region of the laserable assemblage at any one time, so thattransfer of material from the donor element to the receiver element canbe built up one pixel at a time. In this context the term pixelindicates the minimum addressable writing area of the laser exposuresystem. This laser addressable pixel size is generally smaller than theLCD color pixel size described above. Computer control of the writinglaser produces transfer with high resolution and at high speed. Thelaserable assemblage, upon imagewise exposure to a laser as describedsupra, is henceforth termed an imaged laserable assemblage.

For the preparation of images for proofing applications and in photomaskfabrication, the imageable component comprises a colorant. For thepreparation of lithographic printing plates, the imageable componentcomprises an oleophilic material that will receive and transfer ink inprinting.

Laser-induced processes are fast and result in transfer of material withhigh resolution. However, in many cases, the resulting transferredmaterial does not have the required durability. In dye sublimationprocesses, light-fastness is frequently lacking. In ablative and melttransfer processes, poor adhesion and/or durability can be a problem. InU.S. Pat. No. 5,563,019 and U.S. Pat. No. 5,523,192, improved multilayerlaserable assemblages and associated processes are disclosed that doafford improved adhesion and/or durability of the transferred images. InU.S. Pat. No. 6,051,318 an improved donor film for use in the productionof color filters is disclosed. U.S. Pat. No. 6,143,451 discloses alaser-induced thermal image transfer imaging process characterized bythe use of an ejection layer that affords advantages in the final imagedproduct.

As is known in the art, the thermally imageable layer in a laserableassemblage always contains some sort of binder, generally a polymericbinder. The binder serves to hold together the colorant and anyadjuvants thereto before, during and after the image transfer process iseffected, forming a single cohesive, homogeneous mass. It is found thatthe physical properties of the binder have significant effect on theproperties of the transferred image. In particular, it has been found inthe practice of the art that binders characterized by glass transitiontemperatures near or below room temperature provide good toughness anddurability with superior adhesive properties, but often at the expenseof resolution. On the other hand, binders characterized by glasstransition temperatures well above room temperature provide superiorresolution but at the expense of toughness, durability, and adhesion.Practical application of laser-induced thermal image transfer to highresolution applications such as color filter formation requirestoughness and adhesion sufficient to permit survival of the transferredimage during the remainder of the manufacturing process. The resolutionrequirements for the color filter application are extremely demanding,and little trade-off can be made while preserving utility in theapplication.

Aqueous blends of colloidally dispersed polymers for use in makingorganic coatings which are hard and ductile at ambient temperature andwhich remain stiff and elastic at elevated temperature are disclosed inMazur et al, U.S. Pat. No. 6,020,416. The combination of properties isattributed to the use of blends of high molecular weight polymersdiffering in glass transition temperature.

A need exists for stable crosslinked pigmented images on a substratewherein the surface of the image away from the substrate is an extremelysmooth surface.

SUMMARY OF THE INVENTION

Improved products and processes for laser induced thermal imaging aredisclosed herein.

In a first aspect, this invention provides a donor element comprising athermally imageable layer, wherein the thermally imageable layercomprises a crosslinkable binder and a colorant, and wherein thecrosslinkable binder has a number average molecular weight of about1,500 to about 70,000, more typically about 5,000 to about 10,000, andmost typically 10,000 to about 70,000.

In the first aspect, the colorant comprises an aqueous dispersion andthe crosslinkable binder comprises an aqueous dispersion or solution.

In a second aspect, the invention provides a method for making a colorimage comprising:

(1) imagewise exposing to laser radiation a laserable assemblagecomprising:

-   -   (A) a donor element comprising a thermally imageable layer, and    -   (B) a receiver element comprising:        -   (a) a receiver support; and        -   (b) an image receiving layer provided on the surface of the            receiver support; wherein the thermally imageable layer            comprises a crosslinkable binder having a number average            molecular weight of about 1,500 to about 70,000; whereby the            exposed areas of the thermally imageable layer are            transferred to the receiver element to form a            colorant-containing image on the image receiving layer; and

(2) separating the donor element (A) from the receiver element (B),thereby revealing the colorant-containing image on the image receivinglayer of the receiver element.

In the second aspect, the invention further provides a methodcomprising:

(3) applying, typically laminating, the colorant-containing image on theimage receiving layer of the receiver element to a permanent substrate,and removing the receiver support to transfer the colorant-containingimage on the image receiving layer to the permanent substrate. Thereceiver support or the permanent substrate may be made of a transparentmaterial such as glass. Alternately, the image receiving layer comprisesa crosslinkable binder having a number average molecular weight of about1,500 to about 70,000

In the second aspect, the invention also provides a method furthercomprising:

(4) applying, typically laminating, a planarizing film to the imagereceiving layer, and removing the support, wherein the planarizing filmcomprises a support and a planarizing layer. Alternately, theplanarizing layer, image receiving layer or both may comprise acrosslinkable binder having a number average molecular weight of about1,500 to about 70,000. The planarizing layer may have a crosslinkablebinder having a weight average molecular weight of about 20,000 to about110,000, more typically about 30 to about 100,000, and still moretypically about 50,000 to about 85,000.

In a third aspect, the invention provides a method for making a colorimage comprising:

(1) imagewise exposing to laser radiation a laserable assemblagecomprising:

-   -   (A) a donor element having a thermally imageable layer        comprising a crosslinkable binder having a number average        molecular weight of about 1,500 to about 70,000, and    -   (B) a permanent substrate; whereby the exposed areas of the        thermally imageable layer are transferred to the permanent        substrate to form a colorant-containing image on the permanent        substrate; and

(2) separating the donor element (A) from the permanent substrate (B),thereby revealing the colorant-containing image on the permanentsubstrate. The permanent substrate may be glass or treated glass.Alternately, the permanent substrate may be a rigid plastic, e.g.polycarbonate, or a treated rigid plastic.

In a fourth aspect, the invention provides a color liquid crystaldisplay comprising a color filter, wherein the color filter is preparedusing a thermal imaging process, and a donor element comprising athermally imageable layer having a crosslinkable binder and a colorant,wherein the crosslinkable binder has a number average molecular weightof about 1,500 to about 70,000.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of an LCD displayincorporating the color filter of this invention.

FIG. 2 is a simplified schematic diagram of an assemblage comprising adonor element and a receiver element for use in the thermally imagingprocess of the invention.

FIG. 3 illustrates the receiver element of FIG. 2 after exposure andseparation from the donor element, wherein the receiver elementcomprises a receiver support, which may be glass, and carries a colorimage transferred from the thermally imageable layer of the donorelement.

FIG. 4 illustrates the receiver element of FIG. 2 after exposure andseparation from the donor element, wherein the receiver element carriesa color image transferred from the thermally imageable layer of thedonor element, and the transfer of said color image to a permanentsubstrate.

FIG. 5 a is the layout of a drum type thermal imager.

FIG. 5 b is the layout of a flat bed thermal imager.

FIG. 6 shows the orientation of color stripes to the peel direction.

FIG. 7 shows a schematic cross-section of the color filter pattern onglass showing the arrangement of the planarizing layer.

FIG. 8 is an illustration of the lamination stack used for lamination ofthe planarizing layer to the color filter in a press.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, a color filter is prepared bya thermal transfer process, and then overlaid with additional layers toform a liquid crystal display. An assemblage is provided comprising adonor element and a receiver element. Planarizing elements mayoptionally also be used in forming the color filter.

Donor Element

The donor element (10) comprises a thermally imageable layer (12)comprising at least one crosslinkable polymeric binder and a firstcolorant, and a base element. The base element comprises a base support(14) and an optional heating layer (16) between the base support (14)and the thermally imageable layer (12). As best seen in FIG. 2, the basesupport (14) provides support for the heating layer (16), if present,and the thermally imageable layer (12).

Base Support

The base support (14) of the donor element (10) is a dimensionallystable sheet material. Typically, the donor element (10) is flexible tofacilitate subsequent processing steps, as described further, below. Thebase support (14) is transparent to laser radiation to allow forexposure of the thermally imageable layer (12), as described further,below.

Examples of transparent, flexible films appropriate for use as the basesupport (14) include, for example, polyethylene terephthalate(“polyester”), polyether sulfone, polyimides, poly(vinylalcohol-co-acetal), polyolefins, or cellulose esters, such as celluloseacetate, and polyvinyl chloride. Typically, the base support (14) of thedonor element (10) is polyethylene terephthalate that has been plasmatreated to accept the optional heating layer (16). Other materials canbe present as additives in the base support, as long as they do notinterfere with the essential function of the support. Examples of suchadditives include plasticizers, coating aids, flow additives, slipagents, antihalation agents, antistatic agents, surfactants, and otherswhich are known for use in the formulation of films. The base supportgenerally has a thickness in the range of 25–200 microns, preferably38–102 microns.

Heating Layer

As best seen in FIG. 2, the function of the optional heating layer (16)of the donor element (10) is to absorb the laser radiation (L) used toexpose the thermally imageable layer (12) and to convert the radiationinto heat. The heating layer is typically a metal.

Some examples of other suitable materials are transition metal elementsand metallic elements of Groups 13, 14, 15 and 16, their alloys witheach other, and their alloys with the elements of Groups 1 and 2, whichhave less adhesion to the thermally imageable layer (12), or may betreated to have less adhesion, than the adhesion of the thermallyimageable layer (12) to the receiving surface of the substrate (24) andabsorb the wavelength of the laser. The IUPAC numbering system is usedthroughout, where the groups are numbered from left to right as 1–18(CRC Handbook of Chemistry and Physics, 81^(st) Edition, 2000). Tungsten(W) is an example of a suitable transition metal.

Carbon, a Group 14, nonmetallic element, may also be used.

Nickel, aluminum, chromium and nickel vanadium alloys are typical metalsfor the heating layer (16). Chromium applied by sputtering is the mosttypical choice for the heating layer.

Alternatively, in FIG. 2, the optional heating layer (16) can be anorganic layer comprising an organic binder and an infrared absorber.Examples of suitable binders are those that decompose at fairly lowtemperatures when heated such as polyvinyl chloride, chlorinatedpolyvinyl chloride and nitrocellulose. Examples of near infraredabsorbers are carbon black and infrared dyes. Polymers with higherdecomposition temperatures may also be employed in fabricating organicheating layers.

The thickness of the heating layer (16) depends on the opticalabsorption of the metals used. The most preferred metallization is suchas to give 50% optical transmission at 830 nm, with a preferred rangefrom 25% to 60% T.

Although it is preferred to have a single optional heating layer, it isalso possible to have more than one heating layer, and the differentlayers can have the same or different compositions.

The optional heating layer (16) may be applied to the base support (14)by a physical vapor deposition technique. The term “physical vapordeposition” refers to various deposition approaches carried out invacuum. Thus, for example, physical vapor deposition includes all formsof sputtering, including ion beam sputtering, as well as all forms ofvapor deposition, such as electron beam evaporation and chemical vapordeposition. A specific form of physical vapor deposition useful in thepresent invention is RF magnetron sputtering. Nickel may be electronbeam deposited onto the base support (14). Aluminum may be applied byresistive heating. Chromium, nickel and nickel vanadium layers may beapplied by either sputtering or electron beam deposition. In the case ofoptional heating layers comprised of organic layers, the heating layermay be applied by conventional solvent coating techniques.

Thermally Imageable Layer

The thermally imageable layer comprises a crosslinkable binder having anumber average molecular weight of about 1,500 to about 70,000, moretypically about 5,000 to about 10,000, and most typically about 10,000to about 70,000. Typically, the binders are film forming and coatablefrom solution or from a dispersion. Binders having glass transitiontemperatures below about 110° C. are preferred.

It is preferred that the polymeric binder does not self-oxidize,decompose or degrade at the temperature achieved during the laserexposure so that the imageable component and binder are transferredintact for improved durability.

Process steps used to convert color filters into LCD panels ofteninvolve contact of the color filter with organic solvents such asN-methylpyrrolidinone, γ-butyrolactone, acetone, isopropanol, etc. Sincethese solvents swell, or even dissolve, the low molecular weight binderresins used in the thermally imageable layer (12), some form ofcrosslinking capability must be provided. This crosslinking should nottake place to a significant extent until after the thermal imaging step.Premature crosslinking toughens the donor element to an extent that itis more difficult to image.

Some suitable pairs of functional groups for such crosslinking reactionsinclude: hydroxyl and isocyanate; hydroxyl and carboxyl; hydroxyl andmelamine-formaldehyde; carboxyl and melamine-formaldehyde; carboxyl andamine; carboxyl and epoxy, epoxy and amine; and carboxylic anhydride andamine. The epoxy/carboxyl and melamine-formaldehyde/carboxyl pairs areparticularly effective since common aqueous pigment dispersants containcarboxyl groups which also can be incorporated into the finalcrosslinked polymer matrix.

The pairs of crosslinking functional groups can be utilized in severalways. One crosslinking functional group can be incorporated into thebinder polymer backbone, and the other added as a polyfunctional lowmolecular weight crosslinking agent. One crosslinking functional groupcan be incorporated into the binder polymer backbone, and the otherincorporated into a different binder polymer backbone. Both of thecrosslinking functional groups can be incorporated into the same binderpolymer backbone. The desired crosslink density of the final colorfilter dictates relative amounts of the pairs of crosslinking monomers.

Another crosslinking reaction involves one or more of the polymericbinders having pendant groups that are capable of undergoingfree-radical induced or cationic crosslinking reactions. Pendant groupsthat are capable of undergoing free-radical induced crosslinkingreactions are generally those that contain sites of ethylenicunsaturation, such as mono- and poly-unsaturated alkyl groups; acrylicand methacrylic acids and esters. In some cases, the pendantcrosslinking group can be photosensitive, as is the case with pendantcinnamoyl or N-alkyl stilbazolium groups. Pendant groups that arecapable of undergoing cationic crosslinking reactions includesubstituted and unsubstituted epoxide and aziridine groups.

The total binder concentration is generally in the range of about 15–50%by weight, based on the total weight of the thermally imageable layer,preferably 30–40% by weight.

The colorant in the thermally imageable layer may be a pigment or anon-sublimable dye. As is well known in the art, the introduction ofpigments into the film compositions is most readily accomplished byemploying pigment dispersants to prepare stable pigment dispersions. Itis preferred to use a pigment as the colorant for stability and forcolor density, and also for the high decomposition temperature. Thepigment is preferably chosen from pigments having (1) high transparency,and (2) small particle size, wherein the average particle size is lessthan about 100 nanometers. Some useful chemical classes of pigmentsinclude metal-containing phthalocyanines and halogenated derivatives,anthraquinones, pyrazolones, acetoacetyl monoazo, bisazo, and methine.Some examples of transparent pigments that can be used in this inventioninclude RS Magenta 234-007™, GS Cyan 249-0592™ and RS Cyan 248-061, fromSun Chemical Co. (Fort Lee, N.J.); BS Magenta RT-333D™, Microlith Yellow3G-WA™, Microlith Yellow 2R-WA™, Microlith Blue YG-WA™, Microlith BlackC-WA™, Microlith Violet RL-WA™, Microlith Red RBS-WA™, Cromophthal Red3B, Irgalite Blue GLO, and Irgalite Green 6G, from Ciba (Newport, Del.);Fanchon Fast Yellow 5700, from Bayer (Pittsburgh, Pa.); any of theHeucotech Aquis II™ series; any of the Heucosperse Aquis III™ series;and the like.

The amount of colorant present in the thermally imageable layer ischosen such that transmission optical densities of the final colorfilter image prepared upon the permanent substrate satisfactorilyreproduces the required color gamut for the LCD display which will beconstructed using the color filter. The color gamut for LCD displays istypically described using CIE chromaticity coordinates x, y and Y. Whilenot intended to be limiting, typical donor element transmission opticaldensities are in the range from about 1.0 and about 2.5 for red, blueand green at the visible wavelength absorption maxima of the pigments,and between about 3.0 and about 4.0 for black at 550 nm. In general, thecolorant is present in an amount of from about 20 to about 80% byweight, typically about 30 to about 50% by weight, based on the totalweight of the transfer coating.

A dispersant is usually present when a pigment is to be transferred, inorder to achieve maximum color strength, transparency and gloss. Thedispersant is generally an organic polymeric compound and is used toseparate the fine pigment particles and avoid flocculation andagglomeration. A wide range of dispersants is commercially available. Adispersant will be selected according to the characteristics of thepigment surface and other components in the composition as practiced bythose skilled in the art. However, one class of dispersant suitable forpracticing the invention is that of the AB dispersants. The A segment ofthe dispersant adsorbs onto the surface of the pigment. The B segmentextends into the solvent into which the pigment is dispersed. The Bsegment provides a barrier between pigment particles to counteract theattractive forces of the particles, and thus to prevent agglomeration.The B segment should have good compatibility with the solvent used. TheAB dispersants of choice are generally described in “Use of AB BlockPolymers as Dispersants for Non-aqueous Coating Systems”, by H. C.Jakubauskas, Journal of Coating Technology, Vol. 58, No. 736, pages71–82. Suitable AB dispersants are also disclosed in U.K. Patent1,339,930 and U.S. Pat. Nos. 3,684,771; 3,788,996; 4,070,388; 4,912,019;and 4,032,698. Other types of dispersants include graft copolymerdispersants, and random copolymer dispersants. Conventional pigmentdispersing techniques, such as roll milling, media milling, ballmilling, sand milling, etc., can be employed. For color filterapplications, the binder polymer of the thermally imageable layer canalso act as a dispersant for the pigment.

Other materials can be present as additives in the thermally imageablelayer as long as they do not interfere with the essential function ofthe layer. Some examples of such additives include coating aids,plasticizers, flow additives, slip agents, antihalation agents,antistatic agents, surfactants, and others that are known to be used inthe formulation of coatings. However, it is preferred to minimize theamount of additional materials in this layer, as they may deleteriouslyaffect the final product after transfer to the final support.

The thermally imageable layer generally has a thickness in the range ofabout 0.1 to 5 microns, preferably in the range of about 0.1 to 1.5microns. Thicknesses greater than about 5 microns are generally notpreferred as they require excessive energy in order to be effectivelytransferred to the receiver and generally give poorly resolved images.

Although it is typical to have a single thermally imageable layer, it isalso possible to have more than one thermally imageable layer, and thedifferent layers can have the same or different compositions, as long asthey all function as described above. The total thickness of thecombined thermally imageable layers should be in the range given above.

The thermally imageable layer(s) can be coated onto the heating layer ofthe donor, if present, or directly on a support as a dispersion or asolution in a suitable solvent. Any suitable solvent can be used as acoating solvent, as long as it does not deleteriously affect theproperties of the assemblage, using conventional coating techniques orprinting techniques, for example, gravure printing or slot dye coating.

Additional Layers

An ejection layer (not shown) may optionally be provided between theoptional heating layer (16) and the thermally imageable layer (12), asis known in the art. The ejection layer decomposes into gaseousmolecules when heated, providing additional force to cause transfer ofexposed portions of the thermally imageable layer (12) to the receiverelement (20). A polymer having a relatively low decompositiontemperature (less than about 350° C., preferably less than about 325°C., and more preferably less than about 280° C.) may be used. In thecase of polymers having more than one decomposition temperature, thefirst decomposition temperature should be lower than 350° C. Suitableejection layers are disclosed in U.S. Pat. No. 5,766,819, assigned tothe assignee of the present invention. Thermal additives may also beprovided in the ejection layer to amplify the effect of the heatgenerated in the heating layer (16), as is known in the art and alsodescribed in U.S. Pat. No. 5,766,819. U.S. Pat. No. 5,766,819 isincorporated by reference herein. By providing an additionaldecomposition pathway for the creation of gaseous products, additionalpropulsive forces can be generated to assist in the transfer process.

Optionally, there may be a release means (not shown) provided betweenthe heating layer (16), if present, or the support (14) and thethermally imageable layer (12). This may be accomplished by oxygenplasma treating the heating layer (16) or the support (14). Alternately,release layers may be applied to either the heating layer (16), ifpresent, or the support (14) prior to application of the thermallyimageable layer (12). Some useful layers include hexamethyldisilazane(HMDS) available from Arch Chemicals, Inc., Norwalk Conn.,dichlorosilane perfluordecane, available from Gelest, Inc., Tullytown,Pa., tridecafluoro-1,1,2,2-tetrahydooctyl-1-methyldichlorosilane,available from United Chemical Technologies, Inc., Bristol, Pa., etc.Release means may also be a heat activated release material.

Other donor elements may comprise alternate thermally imageable layer orlayers on a support. Additional layers may be present depending of thespecific process used for imagewise exposure and transfer of the formedimages. Some suitable thermally imageable layers over which the overcoatdescribed above may be applied are disclosed in U.S. Pat. No. 5,773,188,U.S. Pat. No. 5,622,795, U.S. Pat. No. 5,593,808, U.S. Pat. No.5,334,573, U.S. Pat. No. 5,156,938, U.S. Pat. No. 5,256,506, U.S. Pat.No. 5,427,847, U.S. Pat. No. 5,171,650 and U.S. Pat. No. 5,681,681.

Receiver Element

The receiver element, illustrated in FIG. 2, comprises a receiversupport (22) and an image-receiving layer (24), and optionally a cushionor release layer (not shown).

The receiver support (22) can be made of the same materials as the basesupport of the donor element. In addition, opaque materials, such aspolyethylene terephthalate filled with a white pigment such as titaniumdioxide, or synthetic paper, such as Tyvek® spunbonded polyolefin may beused as the receiver support. Typical materials for the receiver support(22) are polyethylene terephthalate and polyimide. Alternately, when thereceiver element is used as the permanent substrate, the receiversupport may include transparent plastic films, as described above,glass, and composites thereof. Thin glass substrates (0.5–1.0 mm thick)are typically used.

The image-receiving layer (24) may be a coating of, for example, apolycarbonate; a polyurethane; a polyester; polyvinyl chloride;styrene/acrylonitrile copolymer; poly(caprolactone); vinylacetatecopolymers with ethylene and/or vinyl chloride; (meth)acrylatehomopolymers (such as butyl-methacrylate) and copolymers; and mixturesthereof. This image-receiving layer may be present in any amounteffective for the intended purpose. In general, good results have beenobtained at coating weights of about 1 to about 5 g/m².

In addition to the image-receiving layer, the receiver element mayoptionally include one or more other layers between the receiver supportand the image receiving layer. One additional layer between theimage-receiving layer and the support is a release layer. In theintermediate transfer process where the receiver element is theintermediate transfer element, the release layer can provide the desiredadhesion balance to the receiver element so that the image-receivinglayer adheres to the receiver support during exposure and separationfrom the donor element, but promotes the separation of the imagereceiving layer from the receiver support upon transfer, for example bylamination, of the color image to a permanent support. The color imageis thus between the permanent support (e.g., glass or polarizingelement) and the image receiving layer. The image receiving layer canact as a planarizing layer for the LCD device. Examples of materialssuitable for use as the release layer include polyamides, silicones,vinyl chloride polymers and copolymers, vinyl acetate polymers andcopolymers and plasticized polyvinyl alcohols. The release layer canhave a thickness in the range of 1 to 50 microns. A cushion layer thatis a deformable layer may also be present in the receiver element,typically between the release layer and the receiver support. Thecushion layer may be present to increase the contact between thereceiver element and the donor element when assembled. Examples ofsuitable materials for use as the cushion layer include copolymers ofstyrene and olefin monomers such as styrene/ethylene/butylene/-styrene,styrene/butylene/styrene block copolymers, and other elastomers. Anadhesive layer may be present between the cushion layer and the releaselayer or between the cushion layer and the image receiving layer.Examples of suitable adhesives include hot melt adhesives such asethylene vinyl acetate. Receiving elements suitable for use in colorfilter array applications are disclosed as transfer elements in U.S.Pat. No. 5,565,301 which is hereby incorporated by reference. Typicalpolymers for the receiver layer are (meth)acrylic polymers, including,but not limited to, acrylate homopolymers and copolymers, methacrylatehomopolymers and copolymers, (meth)acrylate block copolymers, and(meth)acrylate copolymers containing other comonomer types, such asstyrene. Alternate receiver elements are disclosed in U.S. Pat. No.5,534,387. Alternately, the image receiving layer may also contain a lowmolecular weight crosslinkable binder similar to that described above.

Typically, the surface of the image receiving layer may be roughened toimprove its function. Methods of roughening the surface of the imagereceiving layer include micro-roughening. Micro-roughening may beaccomplished by any suitable method. One specific example, is bybringing it in contact with a roughened sheet typically under pressureand heat. The pressures used are preferably less than about 8 MPa.Optionally, heat may be applied up to about 80 to about 88° C. moretypically about 54° C. for polycaprolactone polymers and about 94° C.for poly(vinylacetate) polymers, to obtain a uniform micro-roughenedsurface across the image receiving layer. Alternatively, heated orchilled roughened rolls may be used to achieve the micro-roughening.

It is important that the means used for micro-roughening of the imagereceiving layer has uniform roughness across its surface. Typically theaverage roughness (Ra) as determined with a Wyko Profilometer (WykoModel NT 3300, Veeco Metrology, Tucson, Ariz.)) should yield values lessthan about 0.6 micron.

Permanent Substrate

In the intermediate transfer process, the permanent substrate (30) usedin step (3) of the process, which comprises a support (32) and atreatment or coating (34), as shown in FIG. 4, must be opticallytransparent. Some examples include transparent plastic films such aspolyethylene terephthalate and polyimide, glass, treated glass andcomposites thereof, or rigid plastic such as polycarbonate orpoly(4-methylpentene). Thin glass substrates (0.5–1.0 mm thick) may betypically used.

The treatment or coating (34) may be selected from the group consistingof a polycarbonate; a polyurethane; a polyester; polyvinyl chloride;styrene/acrylonitrile copolymer; poly(caprolactone); vinylacetatecopolymers with ethylene and/or vinyl chloride; (meth)acrylatehomopolymers (such as butyl-methacrylate) and copolymers; and mixturesthereof. This layer may be present in any amount effective for theintended purpose. In general, good results have been obtained at coatingweights of about 1 to about 5 g/m².

In the direct transfer process, the receiver element in step (2) is thepermanent substrate (30). The receiver support (22) and an optionalimage-receiving layer (24) comprise the materials described above forthe permanent substrate (30) and the treatment or coating thereon.

It may also be advantageous to employ a substrate that incorporates apre-formed black mask pattern. Typically, a pre-formed black mask isused in the case of rigid glass or plastic substrates, and also can beemployed with flexible permanent substrates or even with flexibleintermediate receiver supports. The black mask, which serves todelineate the colored (e.g. RGB) pixel structure of the color filter,may be prepared in various ways. One method of preparing the black maskmay employ thermal imaging donors of the type described herein. In thiscase the process of constructing the black mask follows the processesdescribed for imaging of the colored donor films to either intermediateor permanent substrates, with or without the optional image receivinglayer.

It is also possible to use a black mask that is preformed on thepermanent substrate by alternate conventional means well known to thoseskilled in the art. An example of a conventional method of producing ablack mask is a photolithographic process involving optical exposure ofa photoresist through an exposure mask. The black mask may be typicallyformed following additional processing steps (e.g. etching, washing,stripping, etc.). When employing a conventional pre-formed black mask,the colored thermal donor elements are exposed and transfer an image tothe permanent substrate (30) with preformed black mask in precisealignment to the preformed black mask. This process results in an‘hybrid’ color filter employing conventional black mask and thermalcolor pattern. The advantage of using a preformed black mask is thatthis process offers improved ease of integration into existing LCDmanufacturing processes. The preformed black mask also takes advantageof the inherently much higher resolution of optical lithographicprocesses in comparison to the thermal transfer process. A highresolution black mask can serve to decrease the resolution requirementof the colored portions of the color filter pattern as the lowerresolution edges of the color patterns are hidden by the black mask.Transfer of the colored donors in alignment with a preformed black maskmay require modification of the thermal imaging equipment to allow ameans for aligning the preformed black mask to the writing locations ofthe imager.

Typically a preformed conventional black mask pattern may be composed ofeither thin (ca. 0.1–0.3 microns) inorganic materials (e.g. chromium,chromium oxide, etc.) or of organic black pigmented resist (organicblack mask). In the case of an organic black mask, typical thicknessesof the black mask layer may be in the range of 0.5–3.0 microns.Generally if the treatment or coating is present with a conventionallyprepared preformed black mask, the treatment or coating will be theoutermost layer of the permanent substrate (30) and will completelycover the preformed black mask.

Process

As shown in FIGS. 2, 5 a and 5 b, the outer surface of the thermallyimageable layer (12) of the donor element (10) is brought into closeproximity with the image receiving layer (24) of the receiving element(20) to form the assemblage (25). Vacuum and/or pressure can be used tohold the donor element (10) and the receiver element (20) together toform the assemblage (25). As another alternative, the donor element (10)and receiver element (20) can be taped together and taped to the imagingapparatus. A pin/clamping system can also be used. Alternatively, thesurface of the donor element and/or the receiver element may beroughened during coating by laminating a matte polyethylene coversheet.This serves improve the average uniformity of the contact between thedonor element (10) and the receiver element (20), by facilitating theevacuation of air from between the donor element (10) and the receiverelement (20).

The assemblage (25) is then exposed through the donor element (10) inselected areas by radiation (L) in the form of heat or light. Asmentioned above, the exposure pattern is the desired pattern of thecolor filter. The optional heating layer (16) or the thermally imageablelayer absorbs the radiation (L), generating heat which causes transferof the heat-exposed portions of the thermally imageable layer (12) tothe receiver element (20).

After exposure, the donor element (10) is separated from the receiverelement (20). This may be done by peeling the two elements apart. Verylittle peel force is typically required; the donor support (10) maysimply be separated from the receiver element (20). Any conventionalmanual or automatic separation technique may be used.

Best quality imaging results are obtained when the process of separatingthe donor and receiver is performed with a consistent peel speed andradius of curvature with the direction of peeling oriented parallel tothe color filter stripe pattern.

After separation of the donor element (10) and the receiver element(20), the color image is transferred to the receiver element, while theunexposed, unwanted portions of the thermally imageable layer (12)remain on the donor element,

The radiation (L) is typically provided by a laser (90). Laser radiationmay be provided at a laser fluence of up to about 1 J/cm², preferablyabout 75–500 mJ/cm². Other techniques that generate sufficient heat tocause transfer of the colorant material layer may be used, as well. Forexample, a thermal print head, or microscopic arrays of metallic tipswith diameters ranging from about 50 nanometers, such as those used inatomic force microscopy, diameters ranging to about 5 microns, may alsobe used. An electric current is provided to the metallic tips togenerate the heat.

Various types of lasers may be used to expose the thermally imageablelayer (12) of colorant material. The laser preferably emits in theinfrared, near-infrared or visible region. Particularly advantageous arediode lasers emitting in the region of 750 to 870 nm which offer asubstantial advantage in terms of their small size, low cost, stability,reliability, ruggedness and ease of modulation. Diode lasers emitting inthe range of 780 to 850 nm are most preferred. Such lasers are availablefrom, for example, Spectra Diode Laboratories, San Jose, Calif. Othertypes of lasers may also be used, as is known in the art, providing thatthe absorption of the heating layer (16) matches the emitting wavelengthof the laser.

As shown in FIG. 5 a, if the donor element (10) and the receiver element(20) are both flexible, the assembly (25) can be conveniently mounted ona drum (37) to facilitate laser imaging.

The transfer step can be repeated with the same receiver element bearingthe first color image (12′) and one or more different donor elementshaving a colorant of a different color, to prepare a multicolor colorfilter pattern. If the receiver support is the permanent substrate, thisforms a color filter (35) as shown in FIG. 3 and FIG. 7. Optionally, anadditional adhesive layer (not shown) may be present on the permanentsubstrate, e.g., glass, before transfer

As best seen in FIG. 4, if the receiver element is an intermediatetransfer element, the next step in the process of the invention is totransfer the color image (12′) from the receiver element to a permanentsubstrate, such as glass. After formation of the color image (12′),which may be a single color or multicolor image, on the receiver element(20), the receiver element (20), including the color image (12′), isbrought into contact with a permanent substrate (30), as shown in FIG.4. The substrate (30) may include a base element (32) and an adhesivecoating (34) to increase the adhesion of the patterned layer (12′) tothe substrate. The adhesive coating (34) may be a suitablepolycarbonate, a polyurethane, a polyester, polyvinyl chloride,styrene/acrylonitrile copolymer, poly(caprolactone), vinylacetatecopolymers with ethylene and/or vinyl chloride, (meth)acrylatehomopolymers (such as butyl-methacrylate), copolymers, and mixturesthereof. Alternately, an image receiving layer similar to that describedabove, for the receiving element, may be applied to the permanentsubstrate, by laminating a separate receiving element to the permanentsubstrate and removing, e.g. peeling, the receiver support, prior totransferring the color image to the permanent substrate.

It is important that the surface of the substrate (30) adjacent thecolor image have greater adhesion to the color image (12′) than theadhesion of the color image and image receiving layer to the receiversupport. The substrate (30) may be any material that will support thesubsequent layers and transmit light generated by the LCD display.Suitable materials include transparent plastic films, as describedabove, glass, and composites. Thin glass substrates are preferred. Glassas thin as 50 microns can be used. The upper limit on thickness is setby the weight and desired properties of the end product. The thicknessis usually less than 5 millimeters. Typical values are from 0.5–1.0 mm.

Preferably, the color image (12′) is transferred to the substrate (30)by lamination. Nip or press lamination may be used, as is known in theart. A roll-to-roll HRL-24 Laminator, manufactured by DuPont,Wilmington, Del., is typically used to accomplish the lamination. Theminimum useful pressure is about 210 kPa. The maximum pressure isdetermined by the pressure at which unwanted contamination, such as aspeck of dust, can cause the substrate to crack. Generally the pressureshould be less than about 69 MPa. After separation of the donor element(10) from the substrate (30), the color image (12′) is transferred tothe substrate to form a color filter element (35).

Planarizing Layer

The next step in the process of the invention is to apply an optionalplanarization layer (40) to the so formed color filter.

The optional planarization layer (40) protects the underlying colorfilter element and smoothes and/or levels the surface. Materials usefulas planarization layers are well known, and generally include polymericmaterials which may be crosslinkable or thermally curable. Some examplesof suitable materials include homopolymers and copolymers of(meth)acrylate esters, such as polyacrylate and polymethylmethacrylate,and their substituted analogs; copolymers of styrene and (meth)acrylateesters, such as styrene/methyl-methacrylate; copolymers of styrene andolefin monomers, such as styrene/ethylene/butylene; copolymers ofstyrene and acrylonitrile; fluoropolymers; copolymers of (meth)acrylateesters with ethylene and carbon monoxide; polycarbonates; polysulfones;polyurethanes; polyesters; and polyimides. The monomers for the abovepolymers can be substituted or unsubstituted. Mixtures of polymers canalso be used. Thermoset materials such as epoxy and amino resins canalso be used. Preferred materials for the planarization layer arecopolymers of methyl methacrylate, butyl methacrylate, methacrylic acid,and glycidyl methacrylate. Low molecular weight polymers are typical forthe planarization layer because of their increased flow under stress.Alternately, the planarizing layer may also contain a low molecularweight crosslinkable binder similar to that described above. In anotherembodiment, the image receiving layer (24) that is transferred with thecolor image (12′) of colorant material may function as the planarizinglayer.

Alternately, the planarizing layer may have a crosslinkable binderhaving a weight average molecular weight of about 20,000 to about110,000, more typically about 30 to about 100,000, and still moretypically about 50,000 to about 85,000 and a composition similar to thatdescribed earlier for the crosslinkable binder in the thermallyimageable layer of the donor element.

The optional planarization layer (40) may be applied using anyconventional coating technique. Such techniques are well known in theart and include spin coating, casting, gravure printing, and extrusioncoating processes. The planarization layer can also be applied as apreformed film by lamination to the color filter element (35) as shownin FIG. 8, wherein a stack comprising a rigid plate (61) such as astainless steel plate; a release element (62) such as a Teflon® sheet; aflexible compressible element (63) such as a fiber reinforced rubbersheet; a polyester sheet (64); the planarizing element having aplanarizing layer (40); color filter (35) with the color filter patternadjacent the planarizing layer (40); a polyester sheet (64′) adjacentthe glass substrate of the color filter; a flexible compressible element(63′) such as a fiber reinforced rubber sheet; a release element (62′)such as a Teflon® sheet; and a rigid plate (61′) such as a stainlesssteel plate; is placed in a vacuum laminator and the chamber evacuatedbefore lamination of the planarizing layer to the color filter element(35) occurs.

Liquid Crystal Display

A simplified schematic representation of a liquid crystal display andcolor filter are shown in FIG. 1. The liquid crystal display comprisestwo panels. The upper panel comprises a first polarizer (71), a glass orother rigid substrate (30), an optional adhesion layer (24), a blackmatrix (12′b) formed by either conventional lithographic techniques, viathermal printing or by other means. The materials comprising the blackmatrix may be either inorganic (e.g. Chromium, Chromium oxide, etc.) ororganic (e.g. black pigmented photoresist). The upper plate furthercomprises the color filter layer comprising separate red, green and bluesub pixels (12′), an optional protective organic planarizing layer (40),a transparent electrical conductor (typically indium tin oxide) (73),and an alignment layer (74) which serves to template the liquid crystalorientation. The upper and lower plates are separated by rigidmechanical spacers (75) that maintain a fixed separation between the twoplates and that further serve to define the cell wherein the liquidcrystal solution is contained (80). The lower plate of the LCD displayis comprised of a second alignment layer (76), transparent conductor(77) and glass or other rigid material as substrate (78) and finally asecond polarizer (72). Not shown in the schematic diagram are the driveelectronics that control the orientation of the liquid crystal. Typicalmodern LCD displays employ an array of thin film transistor circuits(not shown) (one circuit for each RGB sub-pixel) which are fabricated onthe lower plate of the LCD display. Finally, a backlight (79) is locatedbelow the lower plate to provide illumination of the display. LCDdisplays employing reflected ambient illumination may also be used withthe color filters of this invention.

EXAMPLES

These non-limiting examples demonstrate the processes and productsclaimed and described herein. All temperatures throughout thespecification are in ° C. (degrees Centigrade) and all percentages areweight percentages unless indicated otherwise.

Glossary: Abbreviation Description Source Zonyl ® fluoro surfactant; 25%solids DuPont, Wilmington, FSA in water and isopropanol, DE [CAS No.57534-45-7] A lithium carboxylate anionic fluorosurfactant having thefollowing structure: RfCH2CH2SCH2CH2CO2Li where Rf = F(CF2CF2)x andwhere x = 1 to 9 Melinex ® 102 micron clear PET base DuPontTeijin 573Films ™, a joint venture of E. I. du Pont de Nemours & Company Melinex ®Clear PET film base DuPontTeijin LJX-111 Films ™, a joint venture of E.I. du Pont de Nemours & Company Corning display grade glass CorningGlass 1737 Company, Corning, NY VAZO ® DuPont, Wilmington, 67 DECRONAR ® DuPont, Wilmington, 471X DE ELVAX ® DuPont, Wilmington, 550 DEPOLYSTEP Ammonium lauryl sulfate Stepan Co., B-7 Northfield, IL Butyl2-butoxyethanol Aldrich, Milwaukee, Cellosolve WI [111-76-2] 2-amino-2-Aldrich, Milwaukee, methyl-1- WI propanol [124-68-5] N,N- Aldrich,Milwaukee, dimethyl- WI ethanolamine (DMEA) [108-01-0] Irgalite ® Ciba,Newport, DE. Green 6G Chromophthal ® Ciba, Newport, DE. Red 3B MAAMethacrylic acid Aldrich, Milwaukee, WI BzMA benzyl methacrylateAldrich, Milwaukee, WI ETEGMA Triethyleneglycol ethyl ether methacrylatePOEA 2-phenoxyethyl acrylate Aldrich, Milwaukee, WI nBA n-butyl acrylateAldrich, Milwaukee, WI AA acrylic acid Aldrich, Milwaukee, WI MA methylacrylate Aldrich, Milwaukee, WI Joncryl ® Aqueous 30% solids JohnsonPolymer, 63 solution of a styrene acrylic Sturtevant, WI polymer(Joncryl ® 67) with a number average molecular weight of 8200 and weightaverage molecular weight of 12000. Carboset ® Aqueous 43% solids Noveon,Avon Lake, XPD-2091 solution of a styrene acrylic OH resin with weightaverage molecular weight 3250. Aerotex ® Aqueous 85% solution of aNoveon, Avon Lake, 3730 melamine-formaldehyde OH crosslinking agentPigment Dispersions

The commercially available aqueous pigment dispersions listed in Table 1were obtained from Penn Color Inc. (Hatfield, Pa.).

TABLE 1 Pigment dispersions. Color Dispersion Pigment P/D % Solids Blue32S195 (PD-B1) Pigment Blue 15:6 2.0 50.5% Green 32G200 (PD-G1) PigmentGreen 36 2.3 50.0% Red 32R194 (PD-R1) Pigment Red 177 1.5 45.0% Red32R238D (PD-R5) Pigment Red 254 1.5 40.0% Violet 32S212 (PD-V1) PigmentViolet 23 2.3 48.5% Violet 32S168D (PD-V2) Pigment Violet 23 2.0 20.7%Yellow 32Y213D (PD-Y2) Pigment Yellow 74 1.5 42.0% Yellow 32Y145D(PD-Y1) Pigment Yellow 83 2.3 40.0%

Additional commercially available raw materials required for preparationof the donor element are summarized in Table 2.

TABLE 2 Material Abbreviation Source Ammonium hydroxide —2-[2-[2-chloro-3-[[1,3-dihydro-1,1- NIR-1 H. W. Sandsdimethyl-3-(4-sulfobutyl)-2H- (Jupiter, FL)benz[e]indol-2-ylidene]ethylidene]- 1-cyclohexen-1-yl]ethenyl]-1,1-dimethyl-3-(4-sulfobutyl)-1H- benz[e]indolium, inner salt Zinpol ® 20PR-7 Noveon, Cleveland, OH

Tg (Glass transition temperature) values reported are mid-pointtemperatures in degrees Centigrade from DSC scans recorded according toASTM D3418-82.

Molecular weights were measured by standard gel permeationchromatography (GPC) by standard techniques vs. poly(methylmethacrylate) standards in THF solution.

Dynamic light scattering was performed using Brookhaven InstrumentBI-9000AT digital correlator (Brookhaven Instruments, Brookhaven, N.Y.).An argon-ion laser with wavelength 488 nm and power 200 mW was used.Measurements were made at room temperature with scattering angle 60°.The samples were diluted 200 μL into 20 mL water then again 100 μL into20 mL water, and then filtered with 0.45 micron filter. The results arereported as diameter (particle size) in nm units. For generaldiscussions of the determination of particle sizes by quasielastic lightscattering, see Paint and Surface Coatings: Theory and Practice, ed. ByR. Lombourne, Ellis Horwood Ltd., West Sussex, England, 1987, pp.296–299, and The Application of Laser Light Scattering to the Study ofBiological Motion, ed. By J. C. Earnshaw and M. W. Steer, Plenum Press,NY, 1983, pp. 53–76.

Solids content was measured by putting about 5 grams of acrylic latex ina tared, 5-cm aluminum pan, which was placed in a 75° C. vacuum oven atabout 400 mm Hg vacuum for 1 to 2 days. Percent solids was calculated bydividing the final sample weight by the initial sample weight.

Coating weights were measured by cutting out and weighing a 1 dm² pieceof film, removing the coating by rubbing with a paper towel moistened ineither methanol or acetone, drying the film for several minutes, andreweighing. Coating weights are the difference in weights of the beforeand after film in mg, units: mg/dm².

Additional Pigment Dispersions

Pigment dispersions were prepared as described below. The pigmentcompositions of these dispersions are summarized in Table 3.

TABLE 3 Summary of pigment dispersion compositions. Designation PigmentP/D PD-G2 Pigment Green 36 1.5 PD-G3 Pigment Green 36 3.0 PD-K1 DegussaW6220 Carbon Black 2.0 PD-R3 Pigment Red 149 1.5 PD-R4 Pigment Red 1771.5 PD-Y3 Pigment Yellow 83 1.5Pigment Dispersions PD-K1, PD-G2 and PD-G3:

The PD-K1 pigment dispersion was prepared from Degussa W6620 carbonblack and DR-3. The pigment dispersion was prepared at 15% solids with apigment to dispersant ratio (P/D) of 2.0, according to the proceduresdescribed in U.S. Pat. No. 5,231,131, Chu: A mixture of 323.08 grams ofwater, 33.30 grams of dispersant solution, and 3.62 grams of2-amino-2-methyl-1-propanol was charged, along with 40.00 grams ofDegussa W6220 carbon black, to an attritor (Apollo® Trick Titanium,Troy, Mich.). The attritor contained 850 grams of 0.8–1.0 micronzirconia media. The mixture was processed for 22 hours, keeping thetemperature below 38° C. Filtration through a 1 micron filter producedthe pigment dispersion.

Dispersions PD-G2 and PD-G3 were prepared in the same manner as PD-K1using the materials and conditions shown in Table 4.

TABLE 4 Materials and conditions for preparation of pigment dispersionsPD-G2 and PD-G3 Condition PD-G2 PD-G3 Pigment Irgalite ® Green 6GIrgalite ® Green 6G Dispersant DR-3 DR-3 Pigment to Dispersant Ratio 1.53.0 Milling time (hrs) 6 6PD-R3

Red pigment dispersion PD-R3 was prepared with structured acrylicdispersant DR-1 and PV Fast Red B pigment (Clariant Corp., Coventry,R.I.) at a pigment to dispersant ratio of 1.5. The dispersion wasprepared using a 2-roll mill (Lehmann Mills 6×18 Laboratory Mill).Samples of the above described combination of pigment and dispersantwere prepared and milled with diethylene glycol employed as a millingaid. After an appropriate amount of milling time to achieve a uniformmixing, the material was removed from the mill and allowed to cool toroom temperature at which point the material was very brittle and easilycrushed with a mortar and pestle. Typical solids of this chip productwere 86 to 92% with the balance of the solid present as diethyleneglycol.

The isolated chip was then dissolved in water. For this step the chip isagitated at high speed with DMEA to neutralize the dispersant. The chipwas dissolved at approximately 38.5% solids (w/w). After the chip wascompletely dissolved, the solution was diluted with water to 25% solids(w/w) for use donor sheet formulations.

PD-R4

Red pigment dispersion PD-R4 was prepared using Chromophthal® Red 3Bpigment and dispersant DR-4 at a pigment to dispersant ratio of 1.5. Thedispersion was prepared using a horizontal media mill (Eiger Laboratory“Mini” 250 Mill). Samples of the above described combination of pigmentand dispersant were prepared and milled in water at a pigment grindsolids varying from 20% pigment to 30% pigment with good results. Aftermilling for sufficient time to attain good particle size reduction, thedispersion was diluted with water to 25% solids (w/w) for use in donorsheet formulations.

PD-Y3

Yellow pigment dispersion PD-Y3 was prepared using SpectraPAC® WChromafine® Yellow 2727 pigment (Sun Chemical) and dispersant DR-2 at apigment to dispersant ratio of 1.5. The dispersion was prepared using ahorizontal media mill (Eiger Laboratory “Mini” 250 Mill). Samples of theabove described combination of pigment and dispersant were prepared andmilled in water at a pigment grind solids varying from 20% pigment to30% pigment with good results. After milling for sufficient time toattain good particle size reduction, the dispersion was diluted withwater to 25% solids (w/w) for use in donor sheet formulations.

Dispersing Resins

Dispersing Resins DR-1 and DR-4

Pigment dispersants were prepared by group transfer polymerizationtechniques as described in U.S. Pat. No. 5,772,741, Spinelli, to formblock copolymers of the monomer compositions shown in Table 5A. Thenomenclature used in the table indicates that the monomers listed beforethe // were mixed, added to the initiator, and then the monomers afterthe // were added. Dispersant DR-1 was used to make pigment dispersionsin the tetrahydrofuran solvent in which it was prepared, whiledispersant DR-4 was solvent-exchanged with 2-pyrrolidone before use.

TABLE 5 Composition information for GTP dispersing resins. MonomerMonomer Dispersing Resin Components Composition Solvent DR-1 BzMA//MAA13//10 tetrahydrofuran DR-4 BzMA//MAA/ 13//13/7.5 2-pyrrolidone ETEGMADispersing Resins DR-2 and DR-3

Pigment dispersants were prepared by the cobalt chain transfer graftcopolymer methods as described in U.S. Pat. No. 5,231,131, Chu, et. al.Compositions are listed in Table 5B. For each dispersing resin, thecomposition before the -g- was polymerized by cobalt chain transferpolymerization to an oligomer with a polymerizable group at the end.This oligomer was then copolymerized with the remaining monomer mixtureto form a graft copolymer. The DR-2 pigment dispersant was thensolvent-exchanged to produce a solution in 2-pyrrolidone.

TABLE 5B Composition information for SCT dispersing resins. DispersingPolymer Monomer Resin Components Composition Solvent DR-2 POEA-g-66-g-4/30 2-pyrrolidone ETEGMA/MAA DR-3 (69)nBA/MA/AA- (45.5/45.5/9)-g-Methyl ethyl ketone/ g-(31)MMA/MAA (28.75/71.25) isopropanolPolymer ResinsPR-3

Polymer resin, PR-3 was prepared by thoroughly mixing PR-5 and PR-6 in aratio of 85:15 by weight.

Chain Transfer Agent Solution

A chain transfer agent solution (CTA-1) used in the following acryliclatex synthesis was prepared as described by the methods of U.S. Pat.No. 5,362,826, Berge, et. al. and U.S. Pat. No. 5,324,879, Hawthorne.

A 500-liter reactor was equipped with a reflux condenser and nitrogenatmosphere. The reactor was charged with methyl ethyl ketone (42.5 kg)and isopropyl-bis(borondifluorodimethylglyoximato) cobaltate (III) (CoIII DMG) (104 g) and the contents brought to reflux. A first mixture ofCo III DMG (26.0 g), methyl methacrylate (260 kg), and methyl ethylketone (10.6 kg) was added in a first feed to the reactor at a constantrate over a total period of 4 hours. Starting at the same time as thestart of the first feed, a second mixture of VAZO® 67 (5.21 kg) andmethyl ethyl ketone (53.1 kg) was added in a second feed to the reactorat a constant rate over a total period of 5 hours. After the completionof the second feed in 5 hours, the reactor contents were kept at refluxfor a further 30 minutes. After cooling to ambient temperature, a 70 wt% solids solution of the chain transfer agent was obtained.

AR-1

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.40 grams ammonium persulfate in dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 66.0 grams methyl methacrylate,4.0 grams glycidyl methacrylate, and 110.0 grams n-butyl acrylate wasprepared and placed in the addition funnel. A second monomer blend of66.0 grams methyl methacrylate, 4.0 grams glycidyl methacrylate, 110.0grams n-butyl acrylate, and 40.0 grams of methacrylic acid was prepared.While stirring, the contents of the reaction flask was heated to 85degrees Centigrade and maintained at that temperature, within a range of3 degrees centigrade, through the following steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were complete in less thanone minute. The remaining portion of first monomer blend in the additionfunnel was added to the flask, beginning within two minutes, at aconstant rate over a period of 60 minutes. At the end of the addition ofthe first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85 degrees Centigradeplus or minus 3 degrees Centigrade was maintained for 30 minutes afterthe completion of the addition of the initiating solution. Thereafterthe contents of the reaction flask were cooled to ambient temperatureand filtered through a fine paint strainer, (Paul N. Gardner Company,Inc. Pompano Beach, Fla., Item number ST-F 60×48 mesh) to provide theacrylic latex.

The acrylic latex had particle size 88 nm, 33.5% solids, and Tg 4° C.

PR-1, PR-2 and PR-4

An acrylic latex (PR-1) of a controlled molecular weight polymer resinwas prepared as detailed below using the CTA-1 according to the methodin U.S. Pat. No. 5,773,534, Antonelli, et. al. PR-4 was prepared by thesame method using the composition shown in Table 6. A high molecularweight polymer resin (PR-2) was prepared by the same method omitting thechain transfer agent and the composition shown in Table 6.

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.40 grams ammonium persulfate dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 122 grams methyl methacrylate,4.0 grams glycidyl methacrylate, 60.0 grams n-butyl acrylate and 8.0grams CTA-1 was prepared and placed in the addition funnel. A secondmonomer blend of 122.0 grams methyl methacrylate, 4.0 grams glycidylmethacrylate, 60 grams n-butyl acrylate, 12.0 grams of methacrylic acidand 8.0 grams CTA-1 was prepared. While stirring, the contents of thereaction flask were heated to 85° C. and maintained at that temperature,within a range of 3° C., through the following steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were completed in lessthan one minute. The remaining portion of first monomer blend in theaddition funnel was added to the flask, beginning within two minutes, ata constant rate over a period of 60 minutes. At the end of the additionof the first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85° C. plus or minus 3°C. was maintained for 30 minutes after the completion of the addition ofthe initiating solution. Thereafter the contents of the reaction flaskwere cooled to ambient temperature and filtered through a fine paintstrainer, (Paul N. Gardner Company, Inc. Pompano Beach, Fla., Itemnumber ST-F 60×48 mesh) to provide the acrylic latex PR-1. Properties ofthis latex are summarized in Table 6.

The compositions (weight fraction charged to the reactor) and analyticaldata for the polymer resins are summarized in Table 6. Compositions ofthe polymers are in weight percent on polymer solids based on the ChainTransfer Agent, MMA, BA, MAA, and GMA.

TABLE 6 Composition and Analytical Data for Polymer Resins. ParticleDiameter Tg Resin Solids CTA-1 MMA BA MAA GMA (nm) (° C.) Mn Mw PR-133.1 4 61 30 3 2 86 55 2.0 × 10⁴ 8.5 × 10⁴ PR-2 33.4 0 48 40 10 2 91 32— — PR-4 33.0 4 72 15 3 2 74 92 2.6 × 10⁴ 7.4 × 10⁴PR-5

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.40 grams ammonium persulfate dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 90.0 grams methyl methacrylate,4.0 grams glycidyl methacrylate, and 100.0 grams n-butyl acrylate wasprepared and placed in the addition funnel. A second monomer blend of90.0 grams methyl methacrylate, 4.0 grams glycidyl methacrylate, 100.0grams n-butyl acrylate, and 12.0 grams of methacrylic acid was prepared.While stirring, the contents of the reaction flask were heated to 85° C.and maintained at that temperature, within a range of 3° C., through thefollowing steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were complete in less thanone minute. The remaining portion of first monomer blend in the additionfunnel was added to the flask, beginning within two minutes, at aconstant rate over a period of 60 minutes. At the end of the addition ofthe first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85° C. plus or minus 3°C. was maintained for 30 minutes after the completion of the addition ofthe initiating solution. Thereafter the contents of the reaction flaskwere cooled to ambient temperature and filtered through a fine paintstrainer, (Paul N. Gardner Company, Inc. Pompano Beach, Fla., Itemnumber ST-F 60×48 mesh) to provide the acrylic latex PR-5.

This acrylic latex had particle size 81 nm, 33.3% solids, and Tg 113° C.

PR-6

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.20 grams ammonium persulfate dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 10.0 grams methyl methacrylate,20.0 grams styrene, 4.0 grams glycidyl methacrylate, and 160.0 gramsn-butyl acrylate was prepared and placed in the addition funnel. Asecond monomer blend of 10.0 grams methyl methacrylate, 20.0 gramsstyrene, 4.0 grams glycidyl methacrylate, 160.0 grams n-butyl acrylate,and 12.0 grams of methacrylic acid was prepared. While stirring, thecontents of the reaction flask were heated to 85° C. and maintained atthat temperature, within a range of 3 degrees centigrade, through thefollowing steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were complete in less thanone minute. The remaining portion of first monomer blend in the additionfunnel was added to the flask, beginning within two minutes, at aconstant rate over a period of 60 minutes. At the end of the addition ofthe first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85° C. plus or minus 3°C. was maintained for 30 minutes after the completion of the addition ofthe initiating solution. Thereafter the contents of the reaction flaskwere cooled to ambient temperature and filtered through a fine paintstrainer, (Paul N. Gardner Company, Inc. Pompano Beach, Fla., Itemnumber ST-F 60×48 mesh) to provide the acrylic latex, PR-6.

This acrylic latex had a particle size of 81 nm, 33.7% solids, and Tg−21° C.

PR-8

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.40 grams ammonium persulfate in dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 140.0 grams methyl methacrylate,4.0 grams glycidyl methacrylate, and 50.0 grams n-butyl acrylate wasprepared and placed in the addition funnel. A second monomer blend of140.0 grams methyl methacrylate, 4.0 grams glycidyl methacrylate, 50.0grams n-butyl acrylate, and 12.0 grams of methacrylic acid was prepared.While stirring, the contents of the reaction flask was heated to 85° C.and maintained at that temperature, within a range of 3° C., through thefollowing steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were complete in less thanone minute. The remaining portion of first monomer blend in the additionfunnel was added to the flask, beginning within two minutes, at aconstant rate over a period of 60 minutes. At the end of the addition ofthe first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85° C. plus or minus 3°C. was maintained for 30 minutes after the completion of the addition ofthe initiating solution. Thereafter the contents of the reaction flaskwere cooled to ambient temperature and filtered through a fine paintstrainer, (Paul N. Gardner Company, Inc. Pompano Beach, Fla., Itemnumber ST-F 60×48 mesh) to provide the acrylic latex, PR-8.

This acrylic latex had particle size 92 nm, 33.5% solids, and Tg 72° C.

PR-9

A 3-liter, round bottom flask was equipped with a condenser, additionfunnel, initiating solution inlet port, mechanical stirrer, heater andtemperature controller probe, with the contents maintained under anitrogen atmosphere. The flask was charged with 700 grams of deionizedwater and 6.90 grams of POLYSTEP B-7. A first initiating solution of0.40 grams ammonium persulfate in dissolved in 100 mL of deionized waterwas prepared. A first monomer blend of 110.0 grams methyl methacrylate,4.0 grams glycidyl methacrylate, and 80.0 grams n-butyl acrylate wasprepared and placed in the addition funnel. A second monomer blend of110.0 grams methyl methacrylate, 4.0 grams glycidyl methacrylate, 80.0grams n-butyl acrylate, and 12.0 grams of methacrylic acid was prepared.While stirring, the contents of the reaction flask was heated to 85° C.and maintained at that temperature, within a range of 3° C., through thefollowing steps.

The synthesis of the acrylic latex was initiated by the first additionto the flask of 80 mL of the first initiating solution, followed withinone minute by the second addition of 20 mL of the first monomer blendfrom the addition funnel. These two additions were complete in less thanone minute. The remaining portion of first monomer blend in the additionfunnel was added to the flask, beginning within two minutes, at aconstant rate over a period of 60 minutes. At the end of the addition ofthe first monomer blend, the second monomer blend was promptly addedwithin two minutes to the addition funnel and immediately thereafter wasadded to the flask at a constant rate over a period of 60 minutes total.When the addition of the second monomer blend was complete, theremaining initiating solution was promptly added in less than oneminute. Stirring of the contents of the flask at 85° C. plus or minus 3°C. was maintained for 30 minutes after the completion of the addition ofthe initiating solution. Thereafter the contents of the reaction flaskwere cooled to ambient temperature and filtered through a fine paintstrainer, (Paul N. Gardner Company, Inc. Pompano Beach, Fla., Itemnumber ST-F 60×48 mesh) to provide the acrylic latex, PR-9.

This acrylic latex had particle size 94 nm, 33.4% solids, and Tg 39° C.

Donor Formulations

Coating formulations were prepared using the compositions stated in theTables 7A-I. All amounts in Tables 7A-I are listed in grams. Thecoatings are classified according to the molecular weight of the polymerresin binder in Table 7.

TABLE 7 List of coating formulations. Samples designated as lowmolecular weight employ inventive binders. Samples listed as highmolecular weight blends contain binders that are comparative examples.T_(g) of Binder Polymer Formulation Polymer Resin Type (° C.) DF-1B HighMw Blend — DF-1LH Low Mw 92 DF-2B High Mw Blend — DF-2LH Low Mw 92DF-2LL-2 Low Mw 55 DF-2LL Low Mw 55 DF-3B High Mw Blend — DF-3LL Low Mw55 DF-4B High Mw Blend — DF-4LL Low Mw 55 DF-5B High Mw Blend — DF-5LLLow Mw 55 DF-6B High Mw Blend — DF-6LL Low Mw 55 DF-7L Low Mw 73 DF-8LLow Mw 70 DF-9L Low Mw 73

TABLE 7A Donor formulations Formulation Zonyl ® FSA NIR-1 Water PR-3PR-4 PD-R3 PD-R4 DF-1B 0.143 0.156 28.273 10.725 — 18.165 2.836 DF-1LH0.143 0.156 28.273 — 10.725 18.165 2.836

TABLE 7B Donor formulations Zonyl ® Formulation FSA NIR-1 Water PR-1PR-3 PR-4 32S195 32S212 DF-2B 0.180 0.155 38.183 — 12.139 — 8.880 0.463DF-2LH 0.160 0.153 29.383 — — 11.940 17.243 1.122 DF-2LL-2 0.160 0.15329.383 11.940 — — 17.243 1.122 DF-2LL 0.180 0.155 38.183 12.139 — —8.880 0.463

TABLE 7C Donor formulations Formu- Zonyl ® lation FSA NIR-1 Water PR-1PR-3 32G200 PD-Y3 DF-3B 0.180 0.155 38.020 — 4.486 11.880 5.280 DF-3LL0.180 0.155 38.020 4.486 — 11.880 5.280

TABLE 7D Donor formulations Formu- Zonyl ® lation FSA NIR-1 Water PR-1PR-3 32G200 PD-Y3 DF-4B 0.180 0.155 37.180 — 8.446 9.720 4.320 DF-4LL0.180 0.155 37.180 8.446 — 9.720 4.432

TABLE 7E Donor formulations Zonyl ® Formulation FSA NIR-1 Water PR-1PR-3 PD-Y3 PD-G2 PD-G3 DF-5B 0.180 0.155 26.500 — 5.566 6.000 12.0009.600 DF-5LL 0.180 0.155 26.500 5.566 — 6.000 12.000 9.600

TABLE 7F Donor formulations Zonyl ® Formulation FSA Water PR-1 PR-3PD-K1 Zinpol 20 DF-6B 0.100 1.756 — 1.500 8.480 0.668 DF-6LL 0.45910.665 6.872 — 38.919 3.086

TABLE 7G Donor formulation for DF-7L. Ingredient Weight (grams)Distilled water 51.0 Joncryl ® 63 26.0 32S195 19.4 32S212 1.0 Ammoniumhydroxide (3%) 0.7 Zonyl ® FSA 0.4 NIR-1 0.4 Aerotex ® 3730 1.2

TABLE 7H Donor formulation for DF-8L. Ingredient Weight (grams)Distilled water 13695.0 Carboset XPD-2091 1914.0 32S195 2025.0 32S212105.6 Ammonium hydroxide (3%) 69.1 NIR-1 30.6 Aerotex ® 3730 120.1

TABLE 7I Donor formulation for DF-9L. Ingredient Weight (grams)Distilled water 49.9 Joncryl ® 63 18.8 32R238D 22.6 32Y145D 6.5 Ammoniumhydroxide (3%) 0.4 Zonyl ® FSA 0.4 NIR-1 0.4 Aerotex ® 3730 1.1

Additional coating formulations were prepared as summarized in Table 8.The amounts of materials listed in Table 9 were added to a stirred 40 Lstainless steel vessel under air in the order: water, Zonyl® FSA, NIR-1;polymer resin (either pre-neutralized or neutralized with the specifiedamount of 3% ammonium hydroxide immediately prior to use) and pigmentdispersions. The formulations were then stirred for 24–48 hours andfiltered through a 5μ filter.

TABLE 8 Formulations for donor coatings. All weights are listed ingrams. Material CF-1R CF-1B CF-1G CF-1K CF-2R CF-2B CF-2G Film BaseMelinex ® 6442 Melinex ® 473 Melinex ® 473 Melinex ® 473 Melinex ®Melinex ® 453 Melinex ® 453 LJX111 Optical 2.40 @ 473 nm 2.03 @ 610 nm1.73 @ 655 nm 2.99 @ 650 nm 1.97 @ 553 nm 2.23 @ 763 nm 1.53 @ 423 nmDensity(a) 1.45 @ 551 nm 1.99 @ 783      Coating 18 10.6 16.1 18 11.113.9 14.9 weight (mg/dm²) PD-K1 8621.5 PD-B1 — 2131.2 — — — 3853.0 —PD-V1 — 111.2 — — — 201.0 — PD-G1 — — 1265.1 — — — 4073.2 PD-R1 308.6 —— — — — — PD-R2 4263.2 — — — — — — PD-R3 — — 2531.3 — — PD-Y1 — — — —723.2 — 1272.8 PD-Y2 — — 388.8 — PR-1 2647.6 2913.2 1114.5 1555.1 — — —(Neutralized) PR-1 (Acidic) — — — — 1344.7 5255.2 3911.0 Zonyl(r) FSA43.2 43.2 24.0 79.7 36.0 78.1 79.2 Zinpol ® 20 — — — 1110.8 NIR-1 37.237.2 20.6 — 31.0 67.1 68.2Donor Film Bases

Donor films were coated on metallized polyester film base as summarizedin Table 9. All raw polyester base film was provided by DuPont TeijinFilms (Wilmington, Del.). Metal coatings were applied by CP Films Inc.(Martinsville, Va.). Examples of donor films prepared on clean polyesterfilm bases without metal are also described below.

TABLE 9 Base films used in preparation of red, green, blue and blackdonor films employing metal heating layers. The listed film bases weremetallized to 50% visible light transmission with metallic chromium.Film Thickness Base Film (microns) Comments Melinex ® 473 102 —Melinex ® 6442 102 This base incorporates a filter dye absorbing at 670nm (OD = 0.6 +/− 0.1) with OD < 0.1 at 830 nm. Melinex ® LJX111 25 —Melinex ® 453 51 —Coating Conditions

The solutions described in Table 7A-F were coated on Melinex® 473 with50% T Chromium. The coatings were prepared using an automated rod coater(Waterproof® CV Coater, DuPont, Wilmington, Del.) employing a #6 Meyerrod. The coatings were dried at 50° C. for 5 minutes in flowing air.

Formulations DF-7L and DF-9L were coated on 2 mil (50.8 micron) thickun-metallized LJX111 polyester base using the Waterproof® CV Coater witha #5 Meyer rod. The coatings were dried at 50° C. for 5 minutes inflowing air.

The formulations listed in Table 8 were coated onto the specified filmbases using a conventional slot die coating applicator and were dried attemperatures which increased from an initial value of 38° C. to a finalvalue of 65° C. over a period of approximately 5 minutes.

Formulation DF-8L was coated onto both un-metallized Melinex® 573(DF-8L-NM) and onto Melinex® 6442 which was metallized to 50% opticaltransmission with chromium metal (DF-8L-Cr). Coatings were preparedusing a conventional slot die coating applicator as described above. Thecoating weights for DF-8L-NM and DF-8L-Cr were 13.0 and 18.1 mg/dm²,respectively.

Flexible Receiver Films

FR-1

A receiver film (FR-1) was prepared as follows. A coating compositionwas prepared in a 40-Liter stainless steel vessel with the followingingredients: 3241.69 grams of deionized water, 144.08 grams of ZonylFSA, 2161.13 grams of Butyl Cellosolve, 9148.78 grams of PR-8, and21323.13 grams of PR-9, added to the vessel in the stated order. Thecomposition was coated to a dry coating weight of 13.1 mg/dm² on asupporting base. The coating composition was coated on the Elvax® 550surface of a supporting base of 64 micron thick Elvax® 550 (ethylenevinyl acetate copolymer, DuPont) coated onto 102 micron thick Cronar®471X polyester (DuPont, Wilmington, Del.). The coated supporting basewas dried at temperatures which increased from an initial value of about38° C. to a final value of about 65° C. over a period of, about 5minutes. After the film was dried, it was interleaved with OSM mattepolyethylene film (Tredegar Co., New Bern, N.C.) and run at ambienttemperature through nip rolls at 650 kPa to emboss the polyethylenepattern onto the receiver surface. The polyethylene film was left on thereceiver surface until just prior to imaging to prevent contamination ofthe coated surface during subsequent handling.

FR-2

A receiver film was prepared as follows. A coating composition wasprepared in a 40-Liter stainless steel vessel with the followingingredients: 10455.60 grams of deionized water, 36.00 grams of ZonylFSA, 900.00 grams of Butyl Cellosolve, 2607.60 grams of PR-8, 3910.80grams of PR-9 and 90.00 grams of 10% DMEA (w/w) in water, added to thevessel in the stated order. The composition was coated to a dry coatingweight of 12.9 mg/dm² on a supporting base using a conventional slot diecoating applicator as described above. The film base for the coatingcomprised a 102 micron Cronar®471X polyester base (DuPont, Wilmington,Del.) upon which was coated a 32 micron layer composed of 98.75% whiteElvax® 550 chip (whose composition was 95% Elvax® 550/5% rutile titaniumdioxide) and 1.25% blue Elvax® chip (whose composition was 98% Elvax®550/2% Phthalocyanine Pigment Blue 15:3). The coated supporting base wasdried at temperatures which increased from an initial value of about 38°C. to a final value of about 65° C. over a period of about 5 minutes.After the film was dried, it was interleaved with OSM matte polyethylenefilm (Tredegar Co., New Bern, N.C.) and run at ambient temperaturethrough nip rolls at 310 kPa to emboss the polyethylene pattern onto thereceiver surface. The polyethylene film was left on the receiver surfaceuntil just prior to imaging to prevent contamination of the coatedsurface during subsequent handling.

Permanent Substrate

Images prepared via direct to glass imaging were prepared on Corning1737 display grade glass (0.7 mm thick). Prior to thermal imaging of thecolors, a pattern of opaque Chromium grid lines was prepared on theglass using conventional photolithographic processes. The Chromium maskpattern is also frequently referred to as a black mask. The black maskgrid pitch was approximately 90μ×300μ, typical of a conventional XGAdisplay for laptop computing applications. The glass used in imaging wasca. 30 cm×36 cm in size with the black mask pattern covering an area ofca. 20 cm×25 cm.

Prior to preparation of the glass for imaging, the glass was carefullycleaned. Surface debris was first removed by blowing high pressureionized nitrogen gas (SIMCO Top Gun Ionizing Air Gun, Model 4005105).The glass was then washed with soap (Micro® brand cleaner), rinsed withwater, isopropanol and finally with deionized water. The glass was driedunder nitrogen purge. Immediately prior to application of the receiverfilm (see below) the glass was again cleaned with high-pressurenitrogen.

A receiver film for the permanent substrate was prepared as follows. Acoating solution was prepared with the composition shown in Table 10.The coating solution was prepared in water as solvent at 15% solids. Thesolution was coated to a dry coating weight of 30 mg/dm² on a supportingbase using a conventional slot die coating applicator as describedabove. The supporting base was made up of 64 micron thick Elvax® 550(DuPont) coated onto 102 micron thick Cronar® 471X (DuPont). The coatingwas dried at temperatures that increased from an initial value of 38° C.to a final value of 65° C. The smooth surface of the dried film wascovered with a smooth polyethylene coversheet to prevent contaminationof the coated surface during subsequent handling.

TABLE 10 Receiver film composition RF-1. Material Weight (grams) PR-212574.0 Zonyl ® FSA 43.2 N,N- 109.6 Dimethylethanolamine Butylcellosolve 1106.0 Distilled Water 22186.0

The glass permanent substrate was prepared for imaging by lamination ofthe receiver film. The lamination was carried out Riston® Model HRL-24Roll Laminator (DuPont). After removing the cover sheet, the receiverfilm (RF-1) was placed with the coating side in contact with the cleanedsurface of the glass (the surface with the preformed opaque Chromiummask). Lamination was carried out with the rollers heated to 97° C. at aspeed of 0.2 meters/minute. The laminator air feed was adjusted to apressure of 276 kPa. Following lamination, the assembly was allowed tocool completely before removal of the coating support. In practice theremoval of the coating support was generally carried out immediatelyprior to imaging in order to protect the receiver coating surface fromcontamination in handling. After removal of the coating support, thesurface of the receiver coating on glass is very smooth. Measurement ofthe surface roughness of the laminated receiver coating with a WykoModel RST Plus Surface Profiler (Wyko Corp., Tucson, Ariz.) gave anaverage roughness (R_(a)) of 28 nm over a measurement area of 1.08 mm².

Imaging Equipment

Color filter images were prepared utilizing two different versions ofimaging equipment, a drum imager and a flat bed imager.

Drum Imager

The first was a conventional drum type imager comprising a Creo Model3244 Spectrum Trendsetter (Creo Inc., Vancouver, Canada) equipped with a20 W laser head (90) operating at a wavelength of 830 nm. Imaging filmswere exposed to radiation (L) from the back side through the donor filmbase as shown schematically in FIG. 5A. Films were mounted using vacuumhold down to a standard plastic carrier plate (36) clamped mechanicallyto the drum (37). Control of the laser output was under computer controlto build up the desired image pattern. The desired three color image wasbuilt up by sequentially exposing the red, green and blue donor films.The exposure order for the colors can be varied according to othersystem requirements (e.g. optimal exposure characteristics).

Flatbed Imager

The second type of imager (the “flatbed”) employed an identical imaginghead to that on the Spectrum Trendsetter 3244, but the imager was basedon a flatbed format rather than the Trendsetter drum format.

This apparatus, which is particularly useful for imaging with rigidmedia, is shown schematically in FIG. 5B. The sample to be exposed wasmounted using vacuum hold down to a translation stage (37′) positionedbelow the laser head (90). During exposure, the sample was translatedpast the imaging head at a speed of 1.0–1.2 m/s. Following thecompletion of each exposure pass to radiation (L), the imaging head wastranslated in the direction orthogonal to the sample translation to movea new unexposed area of film in front of the laser for the next imagingpass. This process was repeated to build up the completed exposure. Asfor the drum imager, the desired colored image is prepared bysequentially exposing the various colored donor films to the receiversurface of the same permanent substrate.

A modified version of the flatbed imager was also used in preparation ofsome color filter images. This imager differed from that described aboveonly in that the laser imaging head employed a 50 watt laser head. Allimage patterns prepared using this imager were composed of parallelcolored lines with a width of 87 microns on a pitch of 279 microns. Thispattern is representative of features associated with a single color (R,G or B) in typical color filters employed in displays for personalcomputers. In this case, the full RGB color filter pattern employed inthe display would consist of alternating RGB lines 87 microns in widthon a pitch of 279/3=93 microns.

For both the drum based and flatbed imaging systems, laser power wascontrollable and was adjusted in an iterative fashion to optimize imagequality as judged by detailed inspection of the transferred image on thereceiving surface.

Exposure Conditions

The donor films prepared using the coatings listed in Table 7A–F wereimaged using the Trendsetter 3244 Imager. All images were prepared usingreceiver film FR-1. Images consisted of two types of patterns. The firstpattern was composed of an array of parallel lines 105μ in width with apitch of 330μ. This pattern is representative of the color features usedin the preparation of color filters for use in LCD displays. The secondpattern was a grid pattern of 35μ lines with a pitch of 300μ×110μ. Thispattern is representative of the patterns used in preparation of blackmask patterns for color filters for use in LCD displays. The imagingproperties of the films are summarized in Table 11. Image quality wasevaluated based upon microscopic examination of the images formed on thereceiver sheet. Key aspects of image quality include (1) clean sharpedges with no serration, debris, partially adhered fragments of colorcoating (2) well formed image lines with no pinholes or voids, (3)complete transfer of the donor coating so that no residue remains on thedonor sheet after exposure (4) absence of discoloration or surfacecontamination of the images (5) no degradation or decomposition of thetransferred coating (6) good geometric accuracy of the transferred image(7) good adhesion of the transferred image to the receiver film. Theimaged samples were examined using these criteria and assigned imagequality scores were assigned ranging from 1 (poor) to 5 (excellent). Thedata in Table 11 show that in all cases the low molecular weight bindersdelivered as good or better imaging performance than the comparativehigh molecular weight binders.

TABLE 11 Imaging properties of comparative (Type C) and inventive (TypeI) donor films. Exposure conditions were selected so as to compare thebest exposure conditions of each set of films. Drum Laser NominalExposure Image Donor Speed Power Energy Quality Film Type (rpm) (watts)(mJ/cm2) Score DF-1B C 150 9.00 422 3 DF-1LH I 150 8.40 394 4 DF-2B C150 7.00 328 3 DF-2LH I 150 7.25 340 3 DF-2LL-2 I 150 6.85 321 4 DF-2LLI 150 7.75 363 4 DF-3B C 150 7.50 351 2 DF-3LL I 150 6.80 319 3 DF-4B C150 7.30 342 3 DF-4LL I 150 7.30 342 4 DF-5B C 150 7.00 328 1 DF-5LL I150 6.00 281 3 DF-6B C 80 4.75 417 3 DF-6LL I 80 3.55 312 3Preparation of Four-Color Color Filter on Flexible Substrate

A color filter on flexible substrate was prepared by imaging thematerials shown in Table 12 on the Trendsetter 3244. The color filterpattern consisted of parallel stripes of red, green and blue lines thatwere 105μ in width. The colored lines were separated by gaps of 5μ. Thecolored lines were overprinted with a grid of black lines with widths of35μ. The black grid lines were aligned so as to be centered on top ofthe gap between the color stripes. In the direction orthogonal to thecolor lines, the black grid had a pitch of 300μ.

TABLE 12 Exposure parameters for color filter sample prepared onflexible substrate. The receiver film was FR-2. The sample was exposedin the order blue, red, green, black. Parameter CF-1R CF-1B CF-1G CF-1KColor Red Blue Green Black Laser power (watts) 4.50 4.00 3.75 4.00 Drumspeed (rpm) 66.0 66.0 66.0 66.0 Nominal Exposure 495 440 410 440 Energy(mJ/cm²)Lamination of Four-Color Color Filter to Glass Glass Preparation:

Corning 1737 display grade glass (18 cm square) was rinsed withdeionized water, rinsed and gently scrubbed with soapy water (Micro®brand cleaner), rinsed with deionized water, rinsed with isopropanol,rinsed with deionized water, and then dried vertically in a stream ofdry nitrogen at room temperature.

Lamination of Color Filter to Glass:

AR-1 was diluted to 5% solids with water containing 6% butyl cellosolve.This coating mixture was coated onto the prepared glass samples with aspin coater at 1000 rpm. The coated glass was dried at room temperaturefor 24 hours.

The color filter prepared on flexible receiver was laminated to theadhesive-coated glass in a Tetrahedron Model MTP13 laminator at 80° C.for three minutes and 7 MPa pressure. The laminated color filter wasallowed to cool to room temperature and then the backing film was peeledoff to leave the completed color filter image permanently bonded to thesurface of the glass substrate.

Lamination of Planarizing Film to Color Filter on Glass:

A coating composition was prepared by mixing, in order, 4.50 grams ofPR-1, 4.76 grams of water, 0.70 grams of butyl cellosolve, and 0.040grams of Zonyl® FSA. The coating composition was then coated on Melinex®573 base to a thickness of 60 mg/dm² employing the Waterproof® CVcoater. The coating was dried at 50° C. for 5 minutes in flowing air.This planarizing film was then placed coated side down on the colorfilter on glass and then laminated in the Tetrahedron press laminator at130° C. for three minutes at 14 MPa pressure. The planarized colorfilter was then cooled to room temperature before the Melinex® base waspeeled off. The planarized color filter was then annealed in an oven at200° C. for 60 minutes to yield a crosslinked, overcoated color filteron glass.

Preparation of Three-Color Color Filter Directly on Glass with PreformedBlack Mask Exposure Conditions:

Color filter samples on glass were prepared using flatbed imager and theexposure parameters indicated in Table 13. One color filter (CF-1) wasprepared using donors CF-1R, CF-1B and CF-1G and two color filters(CF-2A and CF-2B) were prepared using donors CF-2R, CF-2B and CF-2G.During exposure of the donor films, the ambient environment wasmaintained at a preferred exposure condition of 40±5% RH and 22±2° C.

TABLE 13 Exposure parameters used in production of color filter samples.CF-1 CF- CF- CF-2A and CF-2B Exposure Setting 1R 1B CF-1G CF-2R CF-2BCF-2G Laser Power 6.25 5.50 5.75 4.75 4.50 4.75 (watts) Surface Depth120 85 75 40 72 52 (microns) Swath Width — — — 953 956 959 (microns)Writing Velocity 1.2 1.2 1.2 1.2 1.2 1.2 (meter/sec) Exposure order 3 12 2 3 1Imaging Procedures:

Following the exposure of each donor film, the spent donor was separatedfrom the glass surface in the following manner. This procedure has beenshown to significantly increase image quality of the color filter linepatterns. During the peeling process, a metal rod with diameter of 1.5″was held in firm contact with the donor film. The rod was then used tomaintain a constant radius of curvature of the donor film during thepeeling process. The peeling process was carried out a uniform speed ofabout 1.25 meters/minute. The direction of the peeling process wasarranged parallel to the lines of the color filter pattern as shown inFIG. 6. In FIG. 6, the black mask pattern has been omitted for clarity.The direction of apparent laser motion during the writing process isalso indicated in the FIG. 6.

Planarizing Film

A planarizing film was prepared using the composition listed in Table14. This solution was coated with a #12 Meyer rod to give a driedcoating on Melinex® 573 base. The film was dried for 12 minutes at 50°C. to give a dried coating (82 mg/dm²). Preparation of the planarizingfilm with the low molecular weight polymer resin (PR-1) leads toimproved surface smoothness of the final overcoated color filterassembly.

TABLE 14 Formulation of planarizing film (OC-1). Material Weight (grams)PR-1 (neutralized) 86.62 Zonyl ® FSA 0.14 Butyl cellosolve 7.34Deionized water 5.89

A thinner version of the planarizing film was prepared using theformulation shown in Table 15, coated with a #8 Meyer rod and dried at45° C. for 18 minutes to give a dried coating (3.0 mg/dm²).

TABLE 15 Formulation for thin planarizing film (OC-2). Material Weight(grams) PR-2 (Acidic) 111.75 Zonyl ® FSA 0.50 Butyl cellosolve 12.50Ammonium hydroxide (3% by weight) 2.79 Deionized water 72.46Planarizing Process for Color Filter on Glass

Following the transfer of the color filter pattern to the surface of theglass, it is optional to add a colorless transparent planarizing layer(40) to the surface of the color filter as shown schematically in FIG.7. Various means may be employed to apply this planarizing layer. In oneembodiment the planarizing layer may be laminated from a carrier sheetas described in more detail below. Alternatively the planarizing layermay be applied as a liquid by conventional spin coating technologiesfollowed by thermal drying and annealing to yield the final durableovercoat.

Laminated Planarizing Layer:

The planarizing film described above can be laminated to the finishedcolor filter using either a roll-through lamination process employing alaminator with heated rollers or a press laminator with heated platens.In a typical press lamination a lamination stack was prepared as shownin FIG. 8. The lamination stack was placed in the vacuum laminator(Tetrahedron Model MTP13) and the sample chamber was evacuated to lessthan 5 torr. After evacuation, a series of up to nine bump cycles at 21kPa was carried out to remove any trapped air between the planarizingfilm and the color filter on glass. Lamination was then carried out at atemperature of 110° C. and a pressure of 423 kPa. Hold times varied from3 to 60 minutes.

Application of the planarizing layer by roll through lamination wascarried out using the Riston® Model HRL-24 laminator (DuPont,Wilmington, Del.) at 110° C. with the feed air adjusted to 550 kPa andat a translation speed of 0.1 meter/minute.

Samples were also prepared using an planarizing layer applied by spincoating utilizing conventional techniques. Following application of theplanarizing solution, the samples were heated to completely remove thespin coating solvent.

The overcoating methods for applying an overcoat or planarizing layerused for preparation of LCD display samples are summarized in Table 16.

TABLE 16 Overcoating methods used for color filters used in preparationof LCD display samples. Sample Overcoat method CF-1 Press laminated,thick overcoat OC-1 CF-2A Spin coated overcoat CF-2B Press laminated,thin overcoat OC-2Final Annealing

Prior to incorporation of the color filters into functioning displays,the color filters were annealed at 200° C. for 60 minutes in air. Theannealing process crosslinks the epoxy monomers to yield improvedsolvent resistance and mechanical properties for the annealed colorfilter. Samples that employed laminated overcoats or planarizing layerswere annealed after the application of the layer. Samples which employedspin coated layers were annealed prior to application of the layer.

Incorporation of Color Filters into Liquid Crystal Displays

Color filter samples CF-1, CF-2A and CF-2B were all successfullyincorporated into functional active matrix liquid crystal displays usingtechniques which are well known within the liquid crystal displayindustry (see, for instance “Fundamentals of Active-MatrixLiquid-Crystal Displays”, Sang Soo Kim, Society for Information DisplayShort Course, 2001).

Preparation of Color Filter Patterns on Permanent Receiver SubstratesWithout Receiver Coating

The donor film prepared from formulation DF-7L was exposed on theflatbed imager with 50 W laser head using a pattern of parallel 87microns lines on a pitch of 279 microns. The receiver was untreated 0.7mm thick Corning 1737 glass (cleaned as described above) with noreceiver coating. Exposure and processing conditions are presented inTable 17. The exposure yielded a well-resolved pattern of blue linestransferred to the glass. Following annealing in air to crosslink theimage, a durable blue image on glass was obtained.

The donor film prepared from formulation DF-9L was exposed in the samemanner as that for DF-7L using the conditions presented in Table 17. Awell-resolved image was transferred to glass and was annealed asdescribed above. The result was a pattern of durable red lines on glass.

The donor films prepared from formulation DF-8L (DF-8L-NM and DF-8L-Cr)were imaged as described above for DF-7L employing the conditionspresented in Table 17. Both films yielded well-resolved imagestransferred to glass and were annealed as described above. The resultwas patterns of durable blue lines on glass.

TABLE 17 Laser Power Imaging speed Annealing Donor Film (watts) (m/s)conditions DF-7L 21.5 1.0 230° C., 30 min. DF-9L 23.0 1.0 230° C., 30min. DF-8L-NM 23.0 1.0 200° C., 60 min. DF-8L-Cr 18.5 1.0 200° C., 60min.

1. A method for making a color image comprising: (1) imagewise exposingto laser radiation a laserable assemblage comprising; (A) a donorelement comprising a thermally imageable layer, wherein the thermallyimageable layer comprises a colorant and a crosslinkable binder having anumber average molecular weight of about 10,000 to about 70,000; and (B)a receiver element comprising: (a) a receiver support; and (b) an imagereceiving layer provided on the surface of the receiver support, whereinthe image receiving layer comprises a crosslinkable binder having anumber average molecular weight of about 1,500 to about 70,000, wherebythe exposed areas of the thermally imageable layer are transferred tothe receiver element to form a colorant-containing image on the imagereceiving layer; and (2) separating the donor element (A) from thereceiver element (B), thereby revealing the colorant-containing image onthe image receiving layer of the receiver element.
 2. The method ofclaim 1 further comprising: (3) applying the colorant-containing imageon the image receiving layer of the receiver element to a permanentsubstrate, and removing the receiver support to transfer thecolorant-containing image on the image receiving layer to the permanentsubstrate.
 3. The method of claim 2 wherein the applying is bylamination.
 4. The method of claim 3 wherein the receiver support is aflexible substrate.
 5. The method of claim 2 wherein the permanentsubstrate comprises a glass substrate.
 6. The method of claim 5 whereinthe glass substrate is treated with adhesives or siloxane couplingagents.
 7. The method of claim 2 wherein the permanent substratecomprises a rigid plastic substrate.
 8. The method of claim 7 whereinthe rigid plastic substrate comprises polycarbonate.
 9. The method ofclaim 2 further comprising: (4) applying a planarizing layer to theimage on the permanent substrate.
 10. The method of claim 9 wherein theapplying is by lamination.
 11. The method of claim 9 wherein theplanarizing layer comprises a crosslinkable binder having a weightaverage molecular weight of about 20,000 to about 110,000.
 12. A methodfor making a color image comprising: (1) imagewise exposing to laserradiation a laserable assemblage comprising: (A) a donor element havinga thermally imageable layer comprising a colorant and a crosslinkablebinder having a number average molecular weight of about 10,000 to about70,000; and (C) a permanent substrate comprising a glass substratetreated with adhesives or siloxane coupling agents, whereby the exposedareas of the thermally imageable layer are transferred to the permanentsubstrate to form a colorant-containing image on the permanentsubstrate; and (2) separating the donor element (A) from the permanentsubstrate (C), thereby revealing the colorant-containing image on thepermanent substrate; and (3) applying a planarizing layer to thecolorant-containing image on the permanent substrate.
 13. The method ofclaim 12 wherein the glass substrate supports a pre-formed black maskpattern.
 14. The method of claim 12 wherein the glass substrate thatsupports a pre-formed black mask pattern is treated with adhesives orsiloxane coupling agents.
 15. The method of claim 14 further comprisingapplying an image-receiving layer.
 16. The method of claim 12 furthercomprising applying an image receiving layer.
 17. The method of claim 12wherein the applying is by lamination.
 18. The method of claim 12wherein the planarizing layer comprises a crosslinkable binder having aweight average molecular weight of about 20,000 to about 110,000.
 19. Aliquid crystal display comprising a color filter, wherein the colorfilter comprises a color image prepared by the process of claim
 12. 20.The liquid crystal display of claim 19 wherein the color filtercomprises a glass substrate.
 21. The liquid crystal display of claim 20wherein the glass substrate has a performed black mask pattern thereon.22. The liquid crystal display of claim 21 wherein the color filter hasat least three color images thereon.
 23. The liquid crystal display ofclaim 22 wherein the color images are red, blue and green.
 24. Theprocess of claim 1, wherein the donor element further comprises a baseelement comprising a support and a heating layer.
 25. The process ofclaim 24, wherein the donor element further comprises an ejection orsubbing layer between the support and the heating layer.
 26. The processof claim 1, wherein the crosslinkable binder in the thermally imageablelayer is a polymer prepared by emulsion polymerization or solutionpolymerization.
 27. The process of claim 26 wherein the crosslinkablebinder in the thermally imageable layer is prepared from monomersselected from the group consisting of acrylic acid and esters,methacrylic acid and esters, and styrene.
 28. The process of claim 1wherein the colorant is a pigment.
 29. The process of claim 28, whereinthe pigment is selected from the group consisting of metal-containingphthalocyanines and halogenated derivatives, anthraqulnones,pyrazolones, acetoacetyl monoazos, bisazos, and methines.
 30. A liquidcrystal display comprising a color filter, wherein the color filtercomprises a color a image made by the method of claim 1.